The invention relates to a snowplow blade having spring flaps hinged to a bottom edge of the blade. The flaps are retained in their working positions by pre-tensioned reset springs, and wear bars are fastened to the flaps.
With known spring-flap snowplows, the spring flaps are coupled closely together at the plowblade. A torsion reset spring, supported against the backside of the plowblade, holds each spring flap in its working position. When the spring flaps encounter obstacles in the road surface, the individual spring flaps can deflect against the torsion spring by a clockwise swinging motion. This increasingly tensions the reset spring. Considering that the reset spring is already under considerable pre-tension in the normal working position of the spring flap, it is apparent that the reset springs often rupture after a short operating interval as a result of the shock-like deflecting motions of the spring flaps. Even if the springs do not rupture, there is a reduction in their pre-tensioning.
Attempts have been made to compensate this disadvantage by proper dimensioning of the reset springs. In so doing, a compromise has been necessary. The reset spring has to be strong enough to retain its associated spring flap in its working position with sufficient pre-tension. On the other hand, excessive deformation of the spring must be avoided when the spring flap is in its retracted state. With the torsion springs that are customarily used, this compromise could be achieved only by specially fabricated springs with dimensions closely matched to the spring material. Even so, the springs are frequently destroyed prematurely. Moreover, the force of the reset springs, especially with heavy wet snow, often is not sufficient to return the retracted spring flaps to their working positions.
Additionally, known spring-flap snowplows have the further disadvantage, due to the arrangement of the pivoting axis just behind the plowblade, that there is a considerable undercut of the path of motion of the scraping edges of the spring flaps below the surface being scraped.
By contrast, the present invention aims to improve the action of the reset springs in connection with spring-flap snowplows, especially to avoid an overloading of the reset springs, and further to reduce the undercut of the spring flaps to a neglibible value.